Hello Steve & All,
I see many problems with your idea.  I run quite a few two queens.  I am to
busy now to go into a complicated subject like two queens.  Sorry.
I will highlight problem areas with your idea.  You need lots more brood
area.
Bees WILL  swarm out of two queen hives.  Queens could spend all the time
trying to sting each other thru the excluder. Although a lethel sting most
likely wouldn't happen they *might* spend quite a bit of time they should be
laying eggs trying. Disrupting both hives.  Another possibility is the bees
from one package (both being queenright) would fight when given direct
access thru the excluder at the very first.   Also the bees could kill one
of the queens at any time.  Two queens hives are complicated and need
attention.
I do mine like the method described in most bee books.
Sincerely,
Bob Harrison
Odessa, Missouri